1 # size_max.m4 serial 10 2 dnl Copyright (C) 2003, 2005-2006, 2008-2012 Free Software Foundation, Inc. 3 dnl This file is free software; the Free Software Foundation 4 dnl gives unlimited permission to copy and/or distribute it, 5 dnl with or without modifications, as long as this notice is preserved. 6 7 dnl From Bruno Haible. 8 9 AC_DEFUN([gl_SIZE_MAX], 10 [ 11 AC_CHECK_HEADERS([stdint.h]) 12 dnl First test whether the system already has SIZE_MAX. 13 AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [ 14 gl_cv_size_max= 15 AC_EGREP_CPP([Found it], [ 16 #include <limits.h> 17 #if HAVE_STDINT_H 18 #include <stdint.h> 19 #endif 20 #ifdef SIZE_MAX 21 Found it 22 #endif 23 ], [gl_cv_size_max=yes]) 24 if test -z "$gl_cv_size_max"; then 25 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 26 dnl than the type 'unsigned long'. Try hard to find a definition that can 27 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 28 AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], 29 [#include <stddef.h> 30 #include <limits.h>], [size_t_bits_minus_1=]) 31 AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], 32 [#include <stddef.h>], [fits_in_uint=]) 33 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 34 if test $fits_in_uint = 1; then 35 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 36 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 37 AC_COMPILE_IFELSE( 38 [AC_LANG_PROGRAM( 39 [[#include <stddef.h> 40 extern size_t foo; 41 extern unsigned long foo; 42 ]], 43 [[]])], 44 [fits_in_uint=0]) 45 fi 46 dnl We cannot use 'expr' to simplify this expression, because 'expr' 47 dnl works only with 'long' integers in the host environment, while we 48 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 49 if test $fits_in_uint = 1; then 50 gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 51 else 52 gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 53 fi 54 else 55 dnl Shouldn't happen, but who knows... 56 gl_cv_size_max='((size_t)~(size_t)0)' 57 fi 58 fi 59 ]) 60 if test "$gl_cv_size_max" != yes; then 61 AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], 62 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 63 fi 64 dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after 65 dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with 66 dnl #define by AC_DEFINE_UNQUOTED. 67 AH_VERBATIM([SIZE_MAX], 68 [/* Define as the maximum value of type 'size_t', if the system doesn't define 69 it. */ 70 #ifndef SIZE_MAX 71 # undef SIZE_MAX 72 #endif]) 73 ]) 74 75 dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. 76 dnl Remove this when we can assume autoconf >= 2.61. 77 m4_ifdef([AC_COMPUTE_INT], [], [ 78 AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) 79 ]) 80
